Junko Kimura/Getty Images(WASHINGTON) -- Responding to written questions by the Senate Armed Services Committee, Defense Secretary nominee Chuck Hagel suggested that the Obama administration would be ready to get tough with Iran if diplomacy fails to convince Tehran that it must give up its illicit nuclear ambitions.

In advance of his appearance before Congress next week, Hagel apparently wants to dispel the perception that he is somehow "soft" on Iran, given his previous skepticism of sanctions against the regime while he was a Nebraska senator.

Hagel wrote back to the Senate panel, "While there is time and space for diplomacy, backed by pressure, the window is closing. Iran needs to demonstrate it is prepared to negotiate seriously."

Hagel, who has also been criticized for not showing enough support for Israel, the sworn enemy of Iran, is adopting the White House view that all options are on the table, including military action, if Iran ignores the sanctions and continues its alleged pursuit of a nuclear weapon.

However, not all are convinced that Hagel is being true in his new convictions.

Texas Republican Sen. John Cornyn, who has already said he would vote against Hagel, told his fellow lawmakers, "This sudden and convenient transformation beggars belief. He just wants to win approval from members of this chamber in what we might call a confirmation conversion."